The embodiments described herein relate generally to a fuel nozzle assembly for a combustor and, more particularly, to methods and systems for thermally compliant fuel nozzle assemblies.
At least some known fuel nozzle assemblies for combustors, such as combustors for gas turbines, include circuits for gases and circuits for liquids. In at least some known fuel nozzle assemblies, a liquid fuel conduit is at least partially enclosed in a conduit of a gas circuit, due, for example, to space limitations for the fuel nozzle assembly. The gas circuit, which may include a gaseous fuel plenum, may reach high temperatures relative to the liquid in the liquid circuit. Thus, the fuel circuits within at least some known fuel nozzle assemblies may be subjected to significant thermal differences.
Such thermal differences in the fuel nozzle assembly may increase differential thermal expansion and produce undesirable thermal strains. In addition, such thermal differences tend to cause a temperature of each fluid to move out of a respective desired temperature range. For example, a liquid within the liquid circuit must be maintained below a threshold temperature in order to maintain its state as a liquid.